Universal milling and drilling machines are equipped, as a rule, with a horizontal spindle mounted in the headstock and a vertical milling head, the vertical head being mounted on the exposed face of the headstock. The horizontal spindle or the vertical spindle (when a vertical milling head is employed), as required, is driven by a common main drive through a reversing gearbox. In simpler machine tools, the vertical milling head is bolted onto the flat face of the headstock by hand as required. This type of installation prolongs the downtime of the machine tool, and the manual installation process rules out continuous machining procedures.
Headstocks are already known which, at least in part, obviate some of these disadvantages, wherein the vertical milling head is mounted on a separate plate and that plate is in turn mounted on the end of the headstock by an appropriate joint. After loosening the threaded bolts, which are still required, the vertical milling head is pivoted by a servo motor from an upper or lateral storage position into the endwise operating position, and vice versa. However, in this design, manually operable clamping bolts are still required to lock the vertical milling head to the end of the headstock. Moreover, the above embodiments suffer from the further disadvantage that dirt and chips, for example, can accumulate on the exposed surfaces, i.e., on the face of the headstock and on the corresponding surfaces of the vertical milling head, especially when the vertical milling head is in its stored position, since these two surfaces are then exposed.
A headstock is already known for a universal milling and drilling machine of the type mentioned above (see SHW Brochure UF 5), where a swivel head is mounted on the exposed end of the headstock, the swivel head being disposed so that it can rotate through 180.degree. relative to the headstock, at a 45.degree. upward angle with respect to the horizontal. This swivel head has the horizontal spindle on one end face, while a vertical milling head is screwed in the usual fashion onto the other end face. By rotating the swivel head about an axis of rotation that runs at right angles to the plane inclined at 45.degree., either the horizontal spindle or the vertical spindle can be brought into its working position. After one or the other working spindle has been positioned, a positive or non-positive connection to the output shaft of the main drive is made through a clutch. This headstock has an advantage over the designs described above in that the contact areas between the swivel head and the sloping surface of the headstock are always covered, so that the possibility of contamination of these areas is substantially reduced. Furthermore, positioning of one working spindle or the other is carried out without any manual work steps, so that the changeover from one type of working spindle to the other can be incorporated in a machining program.
However, the comparatively low rate of stock removal of the horizontal spindle is disadvantageous. Moreover, the horizontal spindle can be equipped with a spindle sleeve which can be extended only for a very limited distance, thus limiting machining capability. The machining area of this known headstock is further limited by the fact that the horizontal spindle is located relatively far above the guides of the headstock, and, when working with the horizontal spindle, the cylindrical extension of the housing of the vertical milling head is located immediately above this horizontal spindle, so that machining height is limited vertically. In addition, providing an accessory such as a holder-up, a measuring device or the like is not readily possible directly on such a swivel head.
Headstock designs are known, for example, from German Offenlegungsschriften No. 2,458,399 and 2,613,736, wherein a vertical milling head is mounted on a swivel head, the swivel head being mounted endwise on the headstock in a diagonal plane directed downward at 45.degree.. The vertical spindle is driven by the gearbox output shaft through a bevel gear reversing gearbox of various design. The disadvantage of this arrangement is once again the space requirements arising from the short distance between the horizontal drive shaft for the vertical spindle head and the horizontal spindle.